With the progress and promise of two successful seasons having unraveled over the past few months, the Philadelphia Union fired executive vice president and manager Peter Nowak on Wednesday afternoon.

Speaking to reporters at PPL Park, club CEO Nick Sakiewicz said neither the Union’s 2-7-2 MLS record nor the controversy that has surrounded several surprising and unpopular roster moves led to Nowak’s dismissal. Instead, it was “philosophical differences” that prompted the change.

Nowak’s primary assistant, John Hackworth, will take over on an interim basis. Hackworth previously coached the U.S. Under-17 national team and served as an assistant with the senior side under Bob Bradley before joining Nowak in Philadelphia in 2010.

“This isn’t about wins and losses or performance of the team. We have a very good team. We have very good players,” Sakiewicz said. “This is more about philosophical differences, the way (Union chairman Jay Sugarman) and I envision this club. ... The head coach and ownership aren’t on the same page, and that’s why I felt at this time it was really important to make that change and give John the opportunity.”

Sakiewicz did not offer additional details regarding those differences but did say, “It’s just a matter of certain styles and certain ways and the purpose of who we are and what our brand is, that sometimes you go in different directions.”

Nowak coached the U.S. Olympic team in '08 and is the only person to have won an MLS Cup championship as both a player (Chicago Fire in ’98) and coach (D.C. United in ’04). He was granted complete control when hired by the expansion Union ahead of the ’10 season and appeared to be on track toward building a contender.

Philly was competitive in its inaugural campaign and then made the playoffs last season after finishing just three points off the Eastern Conference lead. While Nowak was heavily invested in the club’s young talent, he had veterans in key positions who proved to be critical assets.

When Freddy Adu arrived last summer, the pieces appeared to be in place. But then it all unraveled.

The acrimonious offseason departure of leading scorer and fan favorite Sébastien Le Toux, traded to the Vancouver Whitecaps for financial considerations, cast a pall over the start of the ’12 season as barbs were exchanged through the press. Goalkeeper Faryd Mondragón left as well and his 20-year-old replacement, Zac MacMath, struggled. Adu failed to click consistently and the offense sputtered.

In May, captain Danny Califf was traded to Chivas USA after weeks of public speculation and tension, suggesting once again that Nowak had difficulty communicating with his players. The Union entered the just-concluded international break with the second-worst record in MLS, having scored just eight goals in 11 league games.

Last week, the roster upheaval continued as Nowak traded forward Danny Mwanga to the Portland Timbers. Mwanga, the first-overall pick of the '10 MLS Draft, tallied seven goals and was a finalist for the rookie of the year award. But he has scored just five since, and his apparent regression represented another source of angst for frustrated Union fans.

Sakiewicz said Wednesday that none of the aforementioned personnel moves “were reasons for this change” and that he detected no “erosion” in fan confidence or support.

Over the weekend, the Edinburgh Evening News claimed Nowak expressed interest in the vacant head coaching position at Scottish Cup winner Heart of Midlothian. Nowak denied the report, but the news didn’t suggest stability in Philadelphia.

“Not good timing,” Sakiewicz said of the news out of Scotland. “No employer, no manager likes to read that the most important guy, your most important asset, is out looking for employment. But it was a rumor and I don’t react to rumors.”

He did add that it was “absolutely not” the reason for Nowak's firing.

Hackworth said he had faith in Philadelphia’s young talent but promised, “There’s a lot that’s going to change.” He’ll lead the Union out against visiting D.C. United on Saturday night.

Nowak was scheduled to coach the MLS All-Star team against Chelsea at PPL Park in late July. MLS executive vice president Nelson Rodriguez said Wednesday that MLS will “take the appropriate time” to consider Nowak’s replacement and an announcement is expected in the near future.